1. Field of the Invention
The present invention relates to a radiographic image detection device and a radiographic imaging system
2. Description of the Related Art
In the field of radiographic imaging for medical diagnosis, there has been widely known a radiographic imaging system in which a subject is irradiated with radiation and an intensity distribution of the radiation transmitted through the subject is detected to obtain a radiographic image of the subject. In a recent radiographic imaging system, there has been developed and used a radiographic image detection device called a “flat panel detector” (hereinafter,.referred to as “FPD”), which is formed as a thin flat plate having a large number of photoelectric conversion elements arranged thereon in a matrix. The FPD detects the radiation transmitted through the subject, photoelectricaly converts the detected radiation into electric signals, and performs image processing on the converted electric signals, thereby obtaining easily and rapidly the radiographic image of the subject.
The radiographic image detection device is broadly classified into a stationary detection device installed as a part of the system at a predetermined position and a portable (cassette type) detection device to be freely carried. From a viewpoint of easiness in carrying and handling, utilization of the cassette type radiographic image detection device has been widely studied recently.
Such a cassette type radiographic image detection device needs to have a power supply installed therein for driving the image detection device, and a built-in battery or a replaceable battery is plausible. There has been actually known such radiographic image detection device that has a replaceable battery therein as a power supply and can be repeatedly used with appropriate replacement of the battery with a new one (for example, refer to JP 2002-181942A).
However, in case that the battery needs to be charged or replaced in the middle of continuous imaging operation, it is preferable from a viewpoint of efficient imaging operation to go to the next imaging operation upon end of charging or replacing the battery. However, concerning photodiodes or thin film transistors (hereinafter referred to as ‘TFT”) comprising the radiographic image detection device, it became obvious that efficiency of the entire radiographing workflow is influenced by these units, since its function and operation do not stabilize immediately after supplying power if the power supply is once stopped.
On the other hand, if power is always supplied to all units of the radiographic image detection device, power consumption increases. This leads to a problem of reduction in operation efficiency due to shorter time of operation, particularly in a radiographic image detection device that is operated by an internal battery without supplying power from an external power source. Consequently, it became obvious that efficiency of the entire radiographing workflow is influenced.
Further, some components included in the radiographic image detection device, such as photodiodes or TFTs, deteriorate within time elapse during power supply. For this reason, if power is kept supplied to these components that deteriorate within time, even while imaging operation is not operated for a long period of time, a problem also arises in that deterioration of these components causes the lifetime of the radiographic image detection device to be shortened.